We have shown only a single molecule of neurotransmitter binding to each channel. Ion channels typically have _________ _______ sites for neurotransmitters and require the binding of more than one neurotransmitter molecule to open or close the channel.

a. single binding
b. multiple binding

a. excitatory postsynaptic potential, EPSP

An __________ __________ __________, or ______, is produced when the movement of ions makes the inside of the cell more positive.

Ion channels at a typical excitatory synapse are specific for cations, having a watery pore large enough to pass both sodium and potassium. In a resting neuron, the electrochemical gradient for sodium is very large and causes sodium to move ______ _____ _____. The electrochemical gradient for potassium causes it to move ____ ____ ____, but the gradient is very small.

Ion channels at a typical inhibitory synapse are specific for chloride and the electrochemical gradient for chloride causes it to move into the cell. Inhibitory postsynaptic potentials _________ neurons making the membrane potential more _________.

a. hyperpolarize, negative
b. depolarize, positive

b. intracellular second messengers

Some neurotransmitters bind to receptors that are separate from ion channels. This process most often leads to production of ______________ __________ _________, which ultimately alter ion channels. Such neurotransmitters are said to act indirectly.

Besides excitation, indirectly-acting neurotransmitters can also produce slow inhibition. The neurotransmitters __________, _________, ______, and ______ can act indirectly as well as directly, depending on the receptor to which they bind.